The present invention pertains to power management within mobile telecommunication systems and more particularly for multicast services.
Mobile telecommunication systems transmit information wirelessly over the air. Power for the transmitted signals is a driving consideration in today's mobile telecommunication services, since the power varies with the distance between the mobile telecommunication station and the user's equipment.
Today multimedia multicast services, which are broadcast wirelessly, require large amounts of power by the telecommunication stations. Typically in such wireless telecommunication systems, common channels are used for system based information and signaling messages to all users. In third generation (3G) telecommunication systems, common channels are being considered for high speed data traffic on the downlink for point-to-multipoint communication in order to provide multimedia broadcast multicast services (MBMS).
Common or broadcast channels are not power controlled and a fixed amount of power is allocated by the Radio Network Controller to provide 95–98% area coverage of the entire cell. Further, not all mobile users within the cell subscribe to broadcast services. However, mobile users requiring multicast services may be anywhere within the cell. Therefore, coverage for multicast services within the cell must be extended to the edges of the cell. The main advantage of using a broadcast channel is that all users inside the coverage area are automatically covered.
In one possible approach, the Radio Network Controller (RNC) counts the number of mobile users within a cell who are subscribed to multimedia services. If the number of such mobile users in the cell is below a threshold, multimedia services are provided using—dedicated radio channels. Otherwise, the services are provided using the broadcast channel for 98% area coverage reliability regardless of where the mobile users are located and whether these users are subject to fading conditions. When the broadcast channel is used, there must be sufficient power for the broadcast channel to provide multicast services for the coverage of the entire cell. Simulation and field test results show that for 98% area coverage reliability, that approximately 15% of the base station power should be allocated to the common channel for data rates of 64 kbps at 1% frame erasure rate. For a 128 kilobits per second data transfer rate, more than 30% of the total power of the base station should be allocated to the common channel.
As a result, it would be advantageous to have a multimedia service implementation where only a subset of the users is served by the broadcast channel with the remainder served by dedicated channels. Partial cell coverage reduces the required broadcast channel power significantly, while the remaining users, when selected appropriately, are better served via dedicated channels.
Accordingly, it would be highly desirable to have a method for assigning multicast users to either dedicated or broadcast channel that minimizes the power required by the base station for supporting multimedia broadcast multicast services.